This is a quite basic question but it confusing. ERP is an abbriviation of Enterprise Resource Planning. So what enterprise resource means and how we can plan it with ERP system?

The idea of ERP was developed based on MRP, Materials Requirements Planning. At first people would like to optimize materials for manufacturing and came it up to work together with System. From financial point of view, this helps to make working capital efficient. Thus ERP enables us to make it happen company wise, including HR, Finance and so on.

SAP is one of the most common software of ERP.

https://ja.wikipedia.org/wiki/%E8%B3%87%E6%9D%90%E6%89%80%E8%A6%81%E9%87%8F%E8%A8%88%E7%94%BB